Method for tracking pollution source in process water

ABSTRACT

A method for tracking a pollution source in process water is presented. Firstly, variation curves of drain water drained from different rinsing tanks are respectively obtained, and a water quality concentration of the drain water drained to a buffer tank is detected, so as to output a water quality variation curve. Then, an analytical comparison is performed on each drain water amount variation curve and the water quality variation curve within a same time interval, so as to output an analytical result of each flow of drain water in a range exceeding a predetermined water quality standard. In this manner, the drain water that exceeds the predetermined water quality standard can be tracked in real-time according to the analytical result, thereby quickly improving the process for discharging the drain water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No(s). 097143511 filed in Taiwan, R.O.C. on Nov.11, 2008, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tracking method, and moreparticularly to a method for tracking a pollution source in processwater.

2. Related Art

Semiconductor, thin film transistor liquid crystal display (TFT-LCD),and other high-tech industries have become major industries in Taiwan.In the high-tech industries, after each process is completed, pure wateror ultra-pure water is used for a great amount of rinsing steps, so asto ensure the stability of the next process, resulting in high waterconsumption in the high-tech industries. Secondly, since it is difficultto obtain water sources and develop water resources due to the specialgeographic environment of Taiwan, and the requirement for the reclaimrate of process water regulated in decrees becomes increasingly strict,it is one of important tasks in the high-tech industries of Taiwan toimprove the reclaim rate of process water when water resources arelimited, so as to reduce the waste of the water resources, therebyachieving water saving and environmental protection policy.

Moreover, if people attach importance to the improvement of the reclaimrate of the process water, but neglect the water quality of thereclaimed water, the application of the reclaimed water will be greatlylimited, and even the quality of the ultra-pure water supply will bepolluted, thereby reducing the production capacity. That is to say, thestability of the water quality of the reclaimed water has great effects.Therefore, it is a problem to be urgently overcome by persons skilled inthe art to compromise the improvement of the reclaim rate of the processwater and the water quality of the reclaimed water.

Rinsing water of a semiconductor wafer factory is taken as an example.Drain water from rinsing tanks for rinsing wafers is respectivelydrained through drains of the different tanks, gathered to a sub-maindrain and a main drain in sequence, and then is drained to anintermediate tank (or called a buffer tank). In practice, the waterquality (for example, conductivity, total organic carbon (TOC), pHvalue, and the like) of the drain water drained from each rinsing tankis not monitored during the draining process, but is monitored after thedrain water is drained to the buffer tank. At this time, if the waterquality of the rinsing drain water measured in the buffer tank satisfiesan allowable standard value set by a reclaiming system, the rinsingdrain water is drained to a process-water reclaiming system, that is, anultra-pure water front end, for reclamation. However, once the waterquality of the rinsing drain water measured in the buffer tank exceedsthe allowable standard value set by the reclaiming system, inconsideration of the yield, the water in the whole tank is guided to awaste water treatment system, and will not be reclaimed.

Briefly, when it is detected that the water in the buffer tank isseriously polluted, the water in the whole tank is directly drained tothe waste water treatment system. As a result, a great amount of wateris wasted. Moreover, since the drain water is drained to the buffer tankafter being gathered through the drains of different sizes, and thewater quality is monitored after the drain water is drained to thebuffer tank, even if it is monitored that the water quality in thebuffer tank exceeds the predetermined allowable standard value, it isimpossible to know which rinsing tank the pollution source comes from.Therefore, it is a problem to be urgently overcome by persons skilled inthe art to compromise the reclaim rate of the drain water and thestability of the water quality of the reclaimed water.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention is a method fortracking a pollution source in process water, so as to compromise thereclaim rate of the drain water and the stability of the water qualityof the reclaimed water, and to track the drain water that exceeds apredetermined water quality standard in real-time, thereby quicklyimproving the process for discharging the drain water.

The present invention provides a method for tracking a pollution sourcein process water, which comprises the following steps. Firstly, aplurality of flows of drain water is respectively drained to a buffertank, and drain water amount variations of the flows of drain waterdrained from different draining tanks are synchronously detected, so asto respectively output a plurality of drain water amount variationcurves corresponding to the flows of drain water. Next, a water qualityconcentration in the buffer tank is detected, so as to output a waterquality variation curve. Then, an analytical comparison is performed oneach drain water amount variation curve and the water quality variationcurve within a same time interval, so as to respectively output ananalytical result corresponding to each flow of drain water in a rangeexceeding a predetermined water quality standard.

The present invention provides a method for reclaiming process water,which comprises the following steps. Firstly, a plurality of flows ofdrain water is respectively drained from a plurality of rinsing tanks toa buffer tank, liquid level variations of the rinsing tanks arerecorded, and a plurality of liquid level variation curves arerespectively drawn. A water quality concentration in the buffer tank issynchronously detected, and a water quality variation curve is drawn.Next, each liquid level variation curve and the water quality variationcurve within a same time interval are respectively superposed. Then, apeak overlap ratio of the water quality variation curve and the liquidvariation curve after each superposition is respectively calculated in arange exceeding a predetermined water quality standard. Afterwards, therinsing tank having a possible pollution source is determined accordingto the peak overlap ratio of each flow of drain water. Finally, aprocess for discharging the drain water at a front end of the process isadjusted and improved as soon as possible, that is, the flow of drainwater of the rinsing tank having the possible pollution source is guidedto a waste water tank, and the flows of drain water of other rinsingtanks are guided to a reclaiming tank, so as to facilitate subsequentreclamation.

Therefore, through the method of the present invention, the drain waterthat exceeds the predetermined water quality standard can be tracked inreal-time, thereby quickly improving the process for discharging thedrain water. In this manner, the water quality of the drain water in thebuffer tank can be quickly stabilized, such that the flows of drainwater are drained to the reclaiming system, that is, back to theultra-pure water front end, and can be reused as ultra-pure water aftersimple water treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below for illustration only, and thusare not limitative of the present invention, and wherein:

FIG. 1 is a schematic flow chart of a method for tracking a pollutionsource in process water according to an embodiment of the presentinvention;

FIGS. 2A-2F are liquid level variation curves obtained by respectivelydetecting liquid level variations in a first rinsing tank to a sixthrising tank according to an embodiment of the present invention;

FIGS. 3A and 3B respectively show a liquid level variation and a waterquality concentration of drain water in a buffer tank according to anembodiment of the present invention; and

FIGS. 4-9 are fingerprint recognized figures obtained by superposing theliquid level variation curves in the first rinsing tank to the sixthrising tank and a water quality variation curve of the buffer tank insequence according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic flow chart of a method for tracking a pollutionsource in process water according to an embodiment of the presentinvention. Referring to FIG. 1, firstly, in Step 102, a plurality offlows of drain water is respectively drained from a plurality of rinsingtanks to a buffer tank. The buffer tank is connected to drain from thedifferent rinsing tanks, and is a water tank disposed at a front end ofthe facility and used for analyzing the water quality of the drain waterdrained to the buffer tank. In Step 104, when the drain water is drainedto the buffer tank, drain water amount variations of the flows of drainwater drained from different draining tanks are respectivelysynchronously detected, so as to respectively output drain water amountvariation curves corresponding to the flows of drain water. A waterquality of at least one of the flows of drain water exceeds a waterquality standard predetermined by a reclaiming system. In Step 106, awater quality concentration in the buffer tank is detected, so as tooutput a water quality variation curve.

Then, in Step 108, an analytical comparison is performed on each drainwater amount variation curve and the water quality variation curvewithin a same time interval, so as to respectively output an analyticalresult corresponding to each flow of drain water in a range exceedingthe predetermined water quality standard. Particularly, firstly, in Step108 a, each drain water amount variation curve and the water qualityvariation curve within the same time interval are respectivelysuperposed, that is, a fingerprint recognized figure is formed.Afterwards, in Step 108 b, in the range exceeding the predeterminedwater quality standard, a peak overlap ratio of the drain water amountvariation curve and the water quality variation curve after eachsuperposition is respectively output. Finally, in Step 108 c, ananalytical result is obtained according to the peak overlap ratio ofeach flow of drain water, that is to say, possibility that each flow ofdrain water has the pollution source can be known according to the peakoverlap ratio. In this manner, with reference to the possibility, a usercan quickly find out the rinsing tank most possibly having the pollutionsource, thereby adjusting the process for discharging the drain water assoon as possible.

Referring to FIG. 1, in Step 110, after the rinsing tank most possiblyhaving the pollution source is found out, an operator at the front endof the process is notified in real-time to adjust and improve theprocess for discharging the drain water, for example, to control anelectric valve for adjusting a flow direction of the drain water. Inthis manner, the water quality of the drain water in the buffer tank canbe gradually stabilized, such that the flows of drain water are drainedto the reclaiming system, that is, back to the ultra-pure water frontend, and can be reused as ultra-pure water after simple water treatment.

FIGS. 2A-2F are liquid level variation curves obtained by respectivelydetecting liquid level variations in a first rinsing tank to a sixthrising tank according to an embodiment of the present invention.Referring to FIGS. 2A-2F, in this embodiment, six rinsing tanks (thefirst to the sixth rinsing tanks) and one buffer tank are used forexplanation and description. Firstly, for example, through electronicsignals of a pneumatic valve or the electric valve provided by aconsole, data captured by the console, or data detected by a wateramount detector, liquid level variations in the first to the sixthrinsing tanks are respectively recorded, and then a plurality of liquidlevel variation curves corresponding to the liquid level variations ofthe first to the sixth rinsing tanks are respectively drawn, as shown inFIGS. 2A-2F. Here, the flows of drain water may be drained from thefirst to the sixth rinsing tanks at different time points. The methodfor recording the liquid level variations of the rinsing tanks is notintended to limit the scope of the present invention, and variations maybe made to the present invention by persons of ordinary skill in theart.

Next, when the liquid level variations of the first to the sixth rinsingtanks are recorded, a liquid level variation and a water qualityconcentration of the drain water in the buffer tank are detected, and aliquid level variation curve and a water quality variation curve aredrawn, as shown in FIGS. 3A and 3B respectively. The water quality maybe, for example, TOC, conductivity, pH value, fluoride ion, or the like.In this embodiment, the monitored water quality of the drain water isTOC. Moreover, each reclaiming system sets a water quality standardvalue, serving as a standard for determining whether to reclaim thedrain water or not. In this embodiment, the set water quality standardis 500 mg/L, as shown by a dashed line of FIG. 3B.

It should be noted that, before the analytical comparison is performed,the drain water amount variation curves of the rinsing tanks or correctthe water quality variation curve of the buffer tank must be selectivelycorrected based on a delay time of each flow of drain water. Therefore,all the curves shown in this embodiment have been corrected based on thedelay time. Particularly, the delay time refers to a time differencebetween a time point at which a pollutant is detected in the rising tankand a time point at which the pollutant has been drained to the buffertank. Secondly, the delay time is calculated by a delay time correctionmethod, that is, calculated through a relation with a plurality of delayfactors such as pipe length, pipe area, pipe curvature, pipeinclination, flow time, flow rate, and flow capacity, and through apredetermined correction method obtained according to requirements. Inother words, the delay time can be calculated by using a formuladepending on the delay factors and the predetermined correction methodaccording to practical requirements such as pipe length, pipe area, pipecurvature, and other conditions. The delay time or the correction methodis not intended to limit the scope of the present invention, andvariations may be made to the present invention by persons of ordinaryskill in the art.

In an unknown situation, the water quality of the drain water drainedfrom one of the rinsing tanks exceeds a predetermined water qualitystandard. In this embodiment, the drain water amount of a certainrinsing tank is randomly changed, and a pollutant such as sodiumchloride (NaCl) is added into the rinsing tank to change the waterquality concentration. Next, each liquid level variation curve and thewater quality variation curve within a same time interval arerespectively superposed, so as to form the fingerprint recognizedfigures as shown in FIGS. 4-9. Particularly, the liquid level variationcurve of the first rinsing tank (as shown in FIG. 2A) and the waterquality variation curve of the buffer tank (as shown in FIG. 3B) aresuperposed, so as to form the fingerprint recognized figure as shown inFIG. 4. Similarly, the liquid level variation curve of the secondrinsing tank (as shown in FIG. 2B), the liquid level variation curve ofthe third rinsing tank (as shown in FIG. 2C), the liquid level variationcurve of the fourth rinsing tank (as shown in FIG. 2D), the liquid levelvariation curve of the fifth rinsing tank (as shown in FIG. 2E), and theliquid level variation curve of the sixth rinsing tank (as shown in FIG.2F) are respectively superposed with the water quality variation curveof the buffer tank (as shown in FIG. 3B), so as to respectively form thefingerprint recognized figures as FIGS. 5-9. In FIGS. 4-9, a thickercurve represents the liquid level variation curve of the rinsing tank,and a thinner curve represents the water quality variation curve of thebuffer tank.

Next, the superposed figures are respectively compared. Firstly,referring to FIG. 4, in the range exceeding the predetermined waterquality standard, peak overlap times of the water quality variationcurve and the liquid level variation curve are calculated. After thecalculation, it is obtained that the peak overlap times in the rangeexceeding the predetermined standard value of 500 mg/L in FIG. 4 are 3.Similarly, the peak overlap times in the range exceeding thepredetermined standard value of 500 mg/L in FIGS. 5-9 are calculated insequence, and are respectively 0, 0, 2, 1, and 0. Afterwards, a peakoverlap ratio is further calculated according to the peak overlap times.Then, a value of possibility that each rinsing tank has the pollutionsource is calculated according to the obtained peak overlap ratio ofeach flow of drain water, so as to determine a rinsing tank having apossible pollution source.

Table 1 shows peak overlap times and values of possibility of thepresence of the pollution source calculated after the liquid levelvariation curves of the first to the sixth rinsing tanks and the waterquality variation curve of the buffer tank are respectively superposedaccording to an embodiment of the present invention. As shown in Table1, in this embodiment, the possibility that the first rinsing tank hasthe pollution source is the highest.

TABLE 1 Peak Overlap Times and Possibility of the Presence of PollutionSource Obtained After Superposition Peak Overlap Possibility of thePresence Times of Pollution Source (%) First Rinsing Tank 3 99 SecondRinsing Tank 0 0 Third Rinsing Tank 0 0 Fourth Rinsing Tank 2 66 FifthRinsing Tank 1 33 Sixth Rinsing Tank 0 0

It can be seen from the data of Table 1 that, in this embodiment, thepossibility that the first rinsing tank has the pollution source is thehighest, so that it can be determined that the first rinsing tank is themost suspicious pollution source. Therefore, after the rinsing tank mostpossibly having the pollution source is found out, an operator at thefront end of the process is notified in real-time to adjust and improvethe process for discharging the drain water, for example, to control anelectric valve for adjusting a flow direction of the drain water. Thatis to say, in this embodiment, for example, the flow of drain water ofthe first rinsing tank is immediately guided to a waste water tank, andthe flows of drain water of the second to the sixth rinsing tanks areguided to a reclaiming tank, and can be reused as ultra-pure water aftersimple water treatment.

Therefore, through the method of the present invention, the drain waterthat exceeds the predetermined water quality standard can be tracked inreal-time, thereby quickly improving the process for discharging thedrain water. In this manner, the water quality of the drain water in thebuffer tank can be quickly stabilized, such that the flows of drainwater are drained to the reclaiming system, that is, back to theultra-pure water front end, and can be reused as ultra-pure water aftersimple water treatment. It can be seen that, through the method of thepresent invention, which rinsing tank the pollution source comes fromcan be quickly and accurately found out without monitoring the waterquality of the drain water of every tank and changing the existingpipelines and devices of the process, thereby improving the process fordischarging the drain water. Thus, the process cost and the labor forcecan further be greatly reduced.

1. A method for tracking a pollution source in process water,comprising: respectively draining a plurality of flows of drain water toa buffer tank, and synchronously detecting drain water amount variationsof the flows of drain water, so as to respectively output a plurality ofdrain water amount variation curves corresponding to the flows of drainwater, wherein a water quality of at least one of the flows of drainwater exceeds a predetermined water quality standard; detecting a waterquality concentration in the buffer tank, so as to output a waterquality variation curve for comparison; and performing an analyticalcomparison on each drain water amount variation curve and the waterquality variation curve within a same time interval, so as to output ananalytical result of each flow of drain water in a range exceeding thepredetermined water quality standard.
 2. The method for tracking thepollution source in the process water according to claim 1, wherein thestep of performing the analytical comparison on each drain water amountvariation curve and the water quality variation curve comprises:respectively superposing each drain water amount variation curve and thewater quality variation curve; outputting a peak overlap ratio of thedrain water amount variation curve and the water quality variation curveafter each superposition in the range exceeding the predetermined waterquality standard; and obtaining the analytical result according to thepeak overlap ratio of each flow of drain water.
 3. The method fortracking the pollution source in the process water according to claim 2,wherein the analytical result is a value of possibility that each flowof drain water has the pollution source.
 4. The method for tracking thepollution source in the process water according to claim 1, wherein thestep of performing the analytical comparison on each drain water amountvariation curve and the water quality variation curve within the sametime interval comprises selectively correcting the drain water amountvariation curves and the water quality variation curve based on a delaytime of each flow of drain water.
 5. The method for tracking thepollution source in the process water according to claim 4, wherein thestep of selectively correcting the drain water amount variation curvesand the water quality variation curve based on the delay time of eachflow of drain water comprises correcting the drain water amountvariation curves and the water quality variation curve through aplurality of delay factors and according to a predetermined correctionmethod.
 6. The method for tracking the pollution source in the processwater according to claim 5, wherein the delay factors are selected fromany combination of pipe length, pipe area, pipe curvature, pipeinclination, flow time, flow rate, and flow capacity.
 7. The method fortracking the pollution source in the process water according to claim 1,wherein the drain water amount variations of the flows of drain waterare detected by a water amount detector.
 8. The method for tracking thepollution source in the process water according to claim 1, wherein thedrain water amount variations of the flows of drain water are dataprovided by a console.
 9. The method for tracking the pollution sourcein the process water according to claim 8, wherein the data provided bythe console is electronic signal outputs of a pneumatic valve orelectronic signal outputs of an electric valve.
 10. The method fortracking the pollution source in the process water according to claim 1,wherein the water quality comprises total organic carbon (TOC).
 11. Themethod for tracking the pollution source in the process water accordingto claim 1, wherein the water quality comprises conductivity.
 12. Themethod for tracking the pollution source in the process water accordingto claim 1, wherein the water quality comprises pH value.
 13. The methodfor tracking the pollution source in the process water according toclaim 1, wherein the water quality comprises fluoride ion.
 14. A methodfor reclaiming process water, comprising: draining a plurality of flowsof drain water from a plurality of rinsing tanks to a buffer tank,wherein a water quality of at least one of the flows of drain waterexceeds a predetermined water quality standard; recording liquid levelvariations of the rinsing tanks, and respectively drawing a plurality ofliquid level variation curves; detecting a water quality concentrationin the buffer tank, and drawing a water quality variation curve;respectively superposing each liquid level variation curve and the waterquality variation curve within a same time interval; respectivelycalculating a peak overlap ratio of the water quality variation curveand the liquid variation curve after each superposition in a rangeexceeding the predetermined water quality standard; determining therinsing tank having a possible pollution source according to the peakoverlap ratio of each flow of drain water; guiding the flow of drainwater of the rinsing tank having the possible pollution source to awaste water tank; and guiding the flows of drain water of other rinsingtanks to a reclaiming tank.
 15. The method for reclaiming the processwater according to claim 14, wherein before the step of respectivelysuperposing each liquid level variation curve and the water qualityvariation curve within the same time interval, the method furthercomprises: selectively correcting the liquid level variation curves andthe water quality variation curve based on a delay time of each flow ofdrain water.
 16. The method for reclaiming the process water accordingto claim 15, wherein the step of selectively correcting the liquid levelvariation curves and the water quality variation curve based on thedelay time of each flow of drain water comprises correcting the drainwater amount variation curves and the water quality variation curvethrough a plurality of delay factors and according to a predeterminedcorrection method.
 17. The method for reclaiming the process wateraccording to claim 16, wherein the delay factors are selected from anycombination of pipe length, pipe area, pipe curvature, pipe inclination,flow time, flow rate, and flow capacity.
 18. The method for reclaimingthe process water according to claim 14, wherein the drain water amountvariations of the flows of drain water are detected by a water amountdetector.
 19. The method for reclaiming the process water according toclaim 14, wherein the drain water amount variations of the flows ofdrain water are data provided by a console.
 20. The method forreclaiming the process water according to claim 19, wherein the dataprovided by the console is electronic signal outputs of a pneumaticvalve or electronic signal outputs of an electric valve.
 21. The methodfor reclaiming the process water according to claim 14, wherein thewater quality comprises total organic carbon (TOC).
 22. The method forreclaiming the process water according to claim 14, wherein the waterquality comprises conductivity.
 23. The method for reclaiming theprocess water according to claim 14, wherein the water quality comprisespH value.
 24. The method for reclaiming the process water according toclaim 14, wherein the water quality comprises fluoride ion.